The Theory of Evolution10/11/11

MA Frameworks 3.3 Explain how mutations in the DNA

sequence of a gene may or may not result in phenotypic change in an organism. Explain how mutations in gametes may result in phenotypic changes in offspring.

MA Frameworks5. Evolution and Biodiversity

Central Concepts: Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

5.1 Explain how evolution is demonstrated by evidence from the fossil record, comparative anatomy, genetics, molecular biology, and examples of natural selection.

MA Frameworks5. Evolution and Biodiversity

5.2 Describe species as reproductively distinct groups of organisms. Recognize that species are further classified into a hierarchical taxonomic system (kingdom, phylum, class, order, family, genus, species) based on morphological, behavioral, and molecular similarities. Describe the role that geographic isolation can play in speciation.

5.3 Explain how evolution through natural selection can result in changes in biodiversity through the increase or decrease of genetic diversity within a population.

What is Evolution? Change over time The process by which modern organisms

descended from ancient organisms Theory: A well supported testable

explanation of phenomena that have occurred in the natural world

Charles Darwin 1809-1882 Born in England (Same day as Abe Lincoln) Traveled around world on ship – Beagle Collected evidence and made observations

that he used to develop ideas that became today’s Theory of Evolution

Key Questions Where did the huge amount of

biodiversity on the Earth come from?

Why are organisms so well suited to the environment that they inhabit?

Darwin & the Galapagos Islands Group of small islands located off South

America Have very different climates, but close together Observed that characteristics of plants and

animals varied among different islands Began to wonder – could these different

animals have come from a common ancestor? Could they have once been members of the same species?

Darwin & the Galapagos Islands

Darwin’s Influences

Around the same time, scientists gained greater understanding of Earth’s changes over time, population growth, and developed primitive Evolution ideas

Darwin’s Influences

James Hutton: Showed that the Earth was far older than a few thousand years

Charles Lyell: Explained the geologic features of Earth shaped over very long time.

J.B. Lamarck: Observed that organisms adapted to environment. Incorrectly proposed that use and disuse of

body part will influence whether passed down to next generation

Darwin’s Influences: Pop. Growth Thomas Malthus: Suggested that if

human population continued to grow rapidly, sooner or later there would not be enough living space or food for everyone

Darwin applied this idea to other organisms

The Origin of Species, 1859

The book that contained Darwin’s ideas about Evolution

Proposed a mechanism for evolution that he called Natural Selection

Provided evidence that Evolution has been happening for millions of years

Early Evolution Controversy

Responding to the Bishop of Oxford, Samuel Wilberforce's question whether he traced his descent from an ape on his mother's or his father's side, Thomas Huxley said:

If then, said I, the question is put to me would I rather have a miserable ape for a grandfather or a man highly endowed by nature and possessing great means and influence and yet who employs those faculties for the mere purpose of introducing ridicule into a grave scientific discussion—I unhesitatingly affirm my preference for the ape.

Natural Selection Premise that organisms stuck in struggle

for existence- food, shelter, resources, etc.

Success depends on ability of an organism to survive and reproduce in its environment – known as Fitness

Fitness results from adaptations – inherited characteristic that increases organisms chance of survival

Natural Selection Is survival of the fittest when the traits

being selected for (whether a trait is good or not) is being determined by fitness in an environment

Results in changes in characteristics of population.

Increases a species fitness over time

Descent with Modification Idea of Darwin’s suggesting that every

living species as descended, with changes, from other species over time.

Principle of Common Descent: All species, living and extinct, were derived from common ancestors.

Evidence for Evolution Fossil Record: See change in organism

structures over time Similar organisms living in similar

environments in places very far apart Homologous body structures:

Structures that changed over time to suit the needs of different species, but that originated as one type of structure (fish fin)

Homologous Structures

Vestigial organs Structures in organisms that may have

served purpose in ancestral species, but no longer have function in current organism

Ex. Human Tailbone

More Evidence: Embryology

The very early stages of development for a wide variety of organisms look the same

Similar cells grow and divide in very similar ways in many species